Pulled the Mess that was my Timing Chain....

OK and I revised my post a couple of times so you might like to re-read it. Personally, I would pull the cam and work carefully. The drilling needs to be done with precision, so doing it with a hand drill in the car is problematic. I would do that in an emergency only.

I really don't know the pin hardness you need but I suspect the equivalent to a grade 5 bolt would do it. The cam bolt ought to do most of the work to hold things still. I have put in hot rodder type cam offset bushings for cam timing in my /6 and they are not particularly hard steel. You can find pin stock in many places and sizes. The trick will be to got just big enough to fit the widest part of the hole but not go too big and break out of the side of the cam; that would not be usable as it would get into the cam bearing. After more thought, I might use a Dremel tool to initially grind the hole inwards towards the sprocket bolt hole.

The pin has probably 'worried' the dowel hole in the direction to retard the cam. So, if you redrill the existing hole to put in a slightly larger dowel, it will likely center in a cam-retarded position. These engines seem fairly sensitive to cam retard and it might be doggy. So that speaks to perhaps another cam or putting in some cam timing bushings to get the cam timing corrected.